Upon arrival at a distribution centre, the goods are unloaded via the boom from the ULDs and sorted for delivery to customers/retailers. The ULDs are then reloaded via the boom with other goods for transportation.
The goods are generally loaded and unloaded using a pivoting telescopic boom conveyor that can be extended telescopically and raised/lowered as required. Goods from the ULD are transferred by hand onto the boom conveyor, which then conveys the goods into the distribution centre via either a travelling conveyor belt or a set of rotating rollers.
In order to transfer goods to and from the boom conveyor, it may be necessary for the operator to stand on a step ladder or platform. However, this is not an ideal solution as it may not be possible for the operator to adjust the height of the stepladder or platform as the height of the boom changes. Also, the use of a stepladder may give rise to safety risks.
It is known to attach an operator platform rigidly to the end of a boom conveyor, allowing an operator to stand at the correct height. This solution is satisfactory when the boom pivots through only a small angle, for example less than 5°. However, if the boom pivots through a larger angle, the floor of the platform may tilt excessively making the operator platform unstable and dangerous to use. This problem is most likely to occur if the boom is relatively short, for example less than 10 meters in length when fully extended.
In the field of mobile access platforms it is known to provide a self-levelling operator platform on an extending boom. Such an apparatus is described for example in EP0581383A. However, the self-levelling mechanism is complex and unsuitable for a boom conveyor that carries a conveyor belt or rollers. Devising a self-levelling mechanism that is simple and reliable, and that is suitable for use on a pivoting boom conveyor is difficult.